The present invention relates to a method and apparatus for processing paper sheets or the like, and more particularly to improvements in a method and apparatus for converting a series of non-overlapping sheets into a stream of partially overlapping sheets, i.e., into a scaly or imbricated stream. Still more particularly, the invention relates to a method and apparatus which can be resorted to for conversion of discrete sheets issuing from a cross cutter into a stream of partially overlapping sheets wherein the leading edge of each next-following sheet overlaps the trailing edge of the preceding sheet.
It is already known to convert a series of separate sheets into a stream of partially overlapping sheets by advancing the sheets of the series at a first speed and by decelerating successive sheets of the series so that each next-following sheet extends forwardly beyond and overlaps the trailing edge of the preceding sheet before it undergoes a braking action in order to accomplish deceleration from the first to the lower second speed. The means for applying an appropriate braking force is normally a rotary member which engages the leading edges of successive sheets of the series. Such apparatus are important and frequently essential components of many processing machines, for example, of cross cutters which serve to subdivide one or more running paper webs into discrete sheets prior to conversion of such sheets into stacks. The stacks are or can be converted into pads, tablets, not books or other stationery products. The cross cutter draws one or more webs from one or more reels or analogous sources and includes cooperating knives and counterknives which sever the web or webs transversely at regular intervals so that each web yields a series of discrete sheets. The sheets of each series are transported to a gathering station and thereupon to a stacking station.
The aforementioned second speed of heretofore known apparatus for conversion of a series of sheets into a stream of partially overlapping sheets is normally a small fraction (e.g., between 30 and 40 percent) of the first speed. Thus, an oncoming sheet of the series travels at a speed which appreciably exceeds the speed of the stream and, therefore, such oncoming sheet must be subjected to a very pronounced braking action. The peripheral speed of the braking member in such conventional apparatus matches the second speed. As a rule, the braking member is a roller which is adjacent to the path of the rearmost sheet of the stream. As mentioned above, the peripheral surface of the rotating roller engages the leading edge of the oncoming foremost sheet of the series and applies a pronounced braking force in order to prevent the oncoming sheet from fully overlapping the preceding sheet or from advancing forwardly and beyond the preceding sheet.
Problems arise when such conventional apparatus are used for the processing of pressure-sensitive material, for example, in connection with the processing of carbon-free copy paper which can be used to make copies solely as a result of the application of mechanical pressure against its surface. In many instances, such carbon-free copy paper is furnished in the form of a continuous web consisting of several superimposed layers. The web is fed into a cross cutter wherein the knives cooperate to sever the web at regular intervals so that the web yields a series of sheets each of which consists of several layers. For example, it is customary to form webs which contain between two and six superimposed layers. When a multi-layer sheet of the series downstream of the cross cutter reaches the aforementioned braking roller of a conventional apparatus for the formation of a stream of partially overlapping sheets, the peripheral surface of the roller engages and applies a pronounced pressure (braking force) against the multi-layer sheet in the region of the leading edge of the sheet and urges the latter against the adjacent sheet or sheets of the stream. This causes at least some reaction fluid to issue from the sheet at the leading edge and to penetrate into the wedge-like gap between the peripheral surface of the braking roller and the stream. The reaction liquid is a conventional constituent of aforediscussed carbon-free copy sheets. The liquid which issues at the leading edge of a multi-layer sheet is not only likely to contaminate the adjacent sheet or sheets of the stream but is even more likely to leave unsightly and highly undesirable depressions or markings in the surface or surfaces of the adjacent sheets because it is urged against such surface or surfaces with a pronounced force, namely, with a force which the braking roller applies to decelerate successive oncoming multi-layer sheets of the series. The markings are more or less pronounced, depending on the composition of the multi-layer sheets and also on the magnitude of the braking force which is applied by the roller.